A physical quantity sensor device of this type typically includes a sensor element for sensing a physical quantity such as an angular velocity or acceleration; the sensor element is mounted on a package. This type of physical quantity sensor device has an application as an angular velocity sensor device or acceleration sensor device.
In such a physical quantity sensor device, a problem occurs in sensor characteristics when an impact from the outside, i.e., an external acceleration is applied thereto.
For example, an angular velocity sensor device senses an angular velocity based on a Coriolis force generated in a sensing direction. However, an acceleration in the sensing direction may be transmitted to a sensor element from the outside via a package even when an angular velocity is not actually applied thereto. Here, an output is produced as though an angular velocity occurred.
With respect to such a physical quantity sensor device, a structure has been conventionally proposed in which a sensor element is held on a package via an elastic member having elasticity such as an adhesive agent or rubber.
Here, the elastic member functions as an anti-vibration member to absorb unnecessary vibration resulting from an external acceleration (see, e.g., PATENT DOCUMENTs 1 to 7).
In such a structure, the external acceleration is attenuated by the elastic function of the elastic member in a path in which the external acceleration is transmitted to the sensor element via the package. The attenuated external acceleration is thus transmitted to the sensor element. Accordingly, this structure may reduce the unnecessary vibration to the sensor element.
In this structure of the physical quantity sensor device, however, it may be difficult to properly perform bonding relative to a component (e.g., sensor element) mounted on the elastic member, or to properly mount the component on the elastic member. This may cause a problem that sufficient assembly cannot be obtained.
FIG. 8 is a view showing a schematic cross-sectional structure of a conventional physical quantity sensor device when, e.g., a low-elasticity adhesive film is used as an elastic member.
In FIG. 8, a circuit board 1300 is mounted on a package 1100 and fixed thereto. A sensor element 1200 is stacked on the circuit board 1300 via an adhesive film 1400 as the elastic member. The sensor element 1200 and the circuit board 1300 are wired with bonding wires 1500 to be electrically connected.
In the conventional physical quantity sensor device, to form a soft adhesion structure for serving as an anti-vibration structure, the low-elasticity adhesive film 1400 is used as the adhesion portion thereof. In the structure, the low-elasticity adhesive film 1400 is used to fix the sensor element 1200 located thereon for an anti-vibration purpose. As a result, the upper portion of the adhesive film 1400 is low in rigidity.
Wire bonding may be performed relative to the mounted component, i.e., sensor element 1200 on the adhesive film 1400, or another component may be mounted in addition to the sensor element 1200. In this case, the holding of the sensor element 1200 becomes unstable so that assembly such as bonding or mounting becomes difficult.
In contrast, to design the structure to be stable during the assembly, the adhesive film 1400 as the elastic member should be hardened. This causes a problem that the elastic function of the adhesive film 1400 is not performed, the amount of attenuation is reduced, and the external acceleration is more likely to be transmitted to the sensor element 1200.                PATENT DOCUMENT 1        JP-H11-218424A        PATENT DOCUMENT 2        JP-H11-264731 A        PATENT DOCUMENT 3        JP-2002-195834 A        PATENT DOCUMENT 4        JP-2002-250627 A        PATENT DOCUMENT 5        JP-2003-21515 A        PATENT DOCUMENT 6        JP-2003-28647 A        PATENT DOCUMENT 7        JP-2003-21647 A        